1. Field of the Invention
This invention relates to colloidal polymer particles containing, metal ions and complexes at concentrations of 0.01 to 3.0 millimoles of metal per gram of polymer solids. The colloidal particles are of relatively uniform size 0.01 to 1.5 micrometers in diameter and are stabilized by charged functional groups. The invention also relates to the preparation of the particles with efficient incorporation of the metal ions and complexes, and the use of the particles for catalysis of chemical reactions in aqueous dispersions.
2. Description of the Prior Art
Colloidal polymer particles have been prepared and used extensively in the formulation of rubbers and coatings. They are generally prepared by the method emulsion polymerization, in which one or more vinyl monomers are dispersed in water with the aid of an ionic surfactant, and polymerization is initiated by thermal, photochemical, or redox formation of free radicals from a peroxy or azo compound. Many variations of the monomer, the emulsifier, and the initiator have been used. It is possible to form stable colloids even in the absence of an emulsifier if the initiator or a charged monomer contributes charged functional groups to the surface of the product particles. The method normally produces spherical particles 0.1 to 1.5 micrometers in diameter if no crosslinking monomer is used in the recipe. The particles may be as small as 0.01 micrometers in diameter if a crosslinking monomer is used.
Preparation of polymer particles with 0.01 to 3.0 millimoles of bound metal ions or complexes per gram of dry polymer requires polymers with at least molar equivalent amounts of counterions. Charged polymer colloids have high concentrations of ionic groups on their surfaces, and those groups may provide no more than about 0.01 to 0.1 millimoles of ionic groups per gram of counterions, depending on the particle size. Any amount of ionic groups in the colloid in excess of the amount needed to cover the surface must be located inside the particles. When the number of charged groups is so large that many are within the particles, the materials are commonly called ion exchange latexes. Ion exchange latexes often contain crosslinking units to prevent their dissolution in water as polyelectrolytes. Such materials have been prepared with the functional groups commonly used in ion exchange resins such as sulfonate ions, carboxylic acids or their salts, amines, and quaternary ammoniums ions, as described by Chong, Isacoff and Neely in U.S. Pat. No. 4,200,695 and by Upson in Journal of Polymer Science, Polymer Symposia, Vol. 72, pp. 45-54 (1985). Ion exchange latexes may be prepared by copolymerization of an ionic monomer with a crosslinking monomer, or by copolymerization of a functional monomer with a crosslinking monomer followed by conversion of the polymerized functional monomer to a charged functional group that serves as the ion exchange site. The monomer mixtures used for copolymerization to ion exchange latexes also often contain a comonomer such as styrene.
Metal complexes in aqueous solutions have been reduced in colloidal metal particles in the presence of water-soluble polymers which stabilize the metal particles in a colloidal state, as described by Hirai in Die Makromolekulare Chemie, Supplement 14, pp 55-69 (1985) and by Fendler in Journal of Physical Chemistry, Vol. 89, pp. 533-537 (1985), but those materials contain metal particles, not individual ions of bound metal complexes of the type of this invention. Metal ions have been trapped in coagulated polymer particles by precipitation of the polymer, as described by Gunesin, Journal of Polymer Science, Polymer Chemistry Edition, Vol. 22, pp. 353-363 (1984) but such a coagulum cannot be redispersed with complete retention of the metal, as can materials of the present invention.
Sun, Yan and Kitano (Macromolecules, Vol. 19, pp. 984-987 (1986) bound copper (II) to a polymer latex that was prepared from styrene, acrylic acid and divinylbenzene and modified by covalent attachment of histamine to part of the acrylic acid units. The copper latex was a catalyst for the air oxidation of ascorbic acid. However, the copolymer was prepared with only 2 percent by weight of acrylic acid, and the method of binding the copper ions to the latex was highly inefficient, since only 2.5 percent of the copper used became attached, and the final concentration of cooper was only 0.0057 millimoles per gram of dry polymer.